1. Field of the Invention
The present invention relates to optical fiber telecommunications cables. More particularly, the present invention relates to a method for accessing an optical fiber in a sheath typically disposed in a telecommunications cable.
2. Description of the Prior Art
Telecommunication cables employing optical fibers are widely used in the telecommunications industry because such optical fibers provide relatively wide bandwidth and low noise operation. Telecommunications cables employing multiple optical fibers are used for a variety of applications including long distance telephone communications, interexchange telephone applications, and other telephony and data transmission applications. Cables containing multiple optical fibers are also being used by cable television networks in the place of traditional coaxial cables containing metallic conductors to provide the bandwidth necessary to support services such as near real-time, on-demand video to the home.
A typical optical fiber cable is formed by one or more cores which contains a plurality of optical fibers and an outer protective jacket surrounding the one or more cores. There are numerous issued U.S. patents that describe various, specific configurations for such cables. In a typical commercially available loose-tube type optical fiber cable, a series of plastic buffer tubes or sheaths are stranded around a central support member in one or more concentric layers. In most commercially available cables, the plastic buffer tubes are provided with a unique color for identification purposes. Also, each of the fibers in a buffer tube are provided with a unique color-coded coating thereon to enable identification of a particular individual fiber from the other fibers within a colored buffer tube of the cable. The color-coding scheme is important when fibers are to be dropped out of the cable to provide a local optical fiber branch.
Cables which are useful in the cable television field typically have a relatively small number of grouped fibers, typically three or four fibers, which are identified, accessed and connected at a drop point. In addition, a large number of spaced apart drop points are typically provided along the length of the cable to enable fibers to be dropped, as required. When a fiber is to be dropped, access to a fiber protected by one of the buffer tubes in the cable is made at a drop point. Typically, access is made by cutting into the outer jacket and using buffer tube cutting or slitting tools to remove a portion of the buffer tube. The use of such tools is necessary for some cable designs because the buffer tube material is tough. On the other hand, some buffer tube or sheath materials are relatively soft and tools are not required. Whether a buffer tube slitting tool is necessary or not, it is important that during the procedure of accessing an optical fiber, other optical fibers are not damaged. Also, once the optical fiber is accessed, it is important to protect the remaining optical fibers in a manner similar to the type of protection provided by the buffer tube. Because the prior methods for accessing the optical fibers typically remove a portion of the buffer tube, the portion of the tube or sheath is no longer available to provide protection to the remaining fibers.